This research concerns the experimental examination of the neural activity in the vestibular system of animals subject to acute, cranial microwave radiation (MWR). This work will proceed initially on mongrel cats, and progress to monkeys as techniques are refined. With the animal immobilized in a stereotaxic frame, we apply MWR to the cranium at an incident frequency of 918 MHz, using power densities in the range of 5 to 80 mW/squared cm squared. The relevant data include gross field and single cell electrical activity in the vestibular nerve and associated nuclei. Interspike intervals are analyzed by computer for average rate and interval statistics, and correlated with the MWR. As a control, known but weak cranial acceleration is applied before and during MWR exposure to classify the unit and field response pattern. Other controls include vestibular nerve section, intracranial temperature monitoring and histological verification of electrode sites. Particular attention is paid to the suppression of MWR induced field artifacts in electrodes and to the calibration of absorbed energy. A secondary aim of this work will be to similarly examine the effects of MWR on unit activity in the auditory pathway.